Vancouver city project aims to put a value on trees

Jeff Lee, Vancouver Sun09.08.2015

Vancouver is stepping up its tree game with a plan to geo-code every street tree in the database and create a special mapping program that will allow residents to geo-locate their own trees on the same map. Eventually, the program will individually quantify the annual “eco impact” of each tree, right down to how much it saves taxpayers in stormwater diversion, energy savings from shading, sequestration of carbon dioxide and filtration of pollutants.

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Vancouver has always had a love affair with trees, to the point that more than two decades ago arborists created a spreadsheet to record the location, type, height and diameter of every one of the city’s 140,000 street trees.

Want to know what that monster is on the southwest corner of Yew Street and 33rd Avenue? In VanTree, an open database the park board created in the 1990s and continually updates, you will find it is one of the city’s biggest horse chestnut trees planted more than 80 years ago.

Now the city is stepping up its tree game with a plan to geo-code every street tree in the database and create a special mapping program that will allow residents to geo-locate their own trees on the same map. Eventually, the program will individually quantify the annual “eco impact” of each tree, right down to how much it saves taxpayers in stormwater diversion, energy savings from shading, sequestration of carbon dioxide and filtration of pollutants.

“What we are trying to do with this strategy is raise the profile of trees to remind people every tree in the city acts together as this cohesive ecosystem to perform these vital functions and make our city livable.”

Although Vancouver has been well ahead of many North American cities in keeping records on what trees it plants, it has not mapped them using global positioning, Isaac said.

Several other cities, including San Francisco, Philadelphia and Seattle have already created interactive maps of their trees.

Making such tree maps available to the public also creates buy-in, according to Doug Wildman, the project director for San Francisco’s Friends of the Urban Forest.

“The population is increasingly more interested in things like this,” he said. “The benefits we see, frankly, are a lot of public relations. People do want to tell us when trees have blown down in a storm or need to be replaced.”

Wildman said San Francisco manages only 40 per cent of the city’s estimated 105,000 trees. Friends of the Urban Forest, a non-profit group with a $1.9 million US budget, helps residents manage the other 60 per cent. That includes planting street trees and caring for them for the first five years. San Francisco’s data is about six years old and is being updated this year.

Vancouver, however, tends to update its tree database weekly as new plantings take place.

Earlier this year, Vancouver issued a request for proposals looking for someone to geo-code, or obtain the GPS co-ordinates of all of its street trees. The city is now reviewing proposals. The plan doesn’t include the estimated 350,000 trees in city parks.

Isaac said she expects the project to be finished in the first three months of 2016. It doesn’t mean the city will tag each tree physically, but rather map their locations using VanTree and city GPS co-ordinates as they relate to nearby houses, streets, property lines and other markers. The results will produce a far more accurate projection of where the trees are and will align with other GPS mapping projects the city does, including the location of engineering services such as water and sewer lines.

The next phase of the project, however, will identify the ecosystem values each tree provides, and make that available to the public, Isaac said. The system now being used by several America cities is called Open Tree Map, which also uses a forestry analysis software called iTree that can quantify the value of individual trees. ITree was developed by the U.S. Department of Agriculture’s forestry service as a tool for urban forest management.

Individual tree information, such as how much energy it saves the city because of the shade it provides or how much storm water it pulls out of the ground, may seem a bit esoteric. But Isaac said it is a good tool for calculating the value both the city and its citizens place a tree.

It also could lead to development and planning policies, especially as the city experiences rapid change through densification and destruction of trees on private property.

The fast pace of redevelopment and a city bylaw allowing residents to chop down one healthy tree annually without reason has eaten deeply into the city’s inventory. In 1995, the tree canopy was estimated to cover 22.5 per cent of the city. By last year it had declined to 18 per cent. That, despite a mandate by Mayor Gregor Robertson’s Vision Vancouver council to plant 150,000 new trees by 2020 as part of their Greenest City Action Plan.

When it brought in its new “urban forest strategy” in 2014, the city changed the rules to limit private tree removals to trees that are “dead, diseased, dying, hazardous or causing property damage.”

The city has already started to look at the “eco value” of its urban trees. A report done by B.A. Blackwell & Associates last year looked at how trees affect air quality, stormwater retention and other issues. It calculated the forest had a total benefit of $2.14 million, including sequestering 20,000 metric tonnes of carbon dioxide valued at nearly $500,000; 34 tonnes of particulate matter valued at $1.35 million, and 125 tonnes of greenhouse gases valued at $300,000.

It also showed that the city’s street trees intercept about 118 million litres of storm water annually.

It identified the top performing species of trees as ones Vancouverites will be familiar with: horse chestnut, linden, maple, elm, birch, London plane and oak.

Isaac said the proposed open tree mapping project will include those valuations. The city is also looking at how homeowners will be able to upload photos and notes about trees on the map.

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Vancouver city project aims to put a value on trees

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